GH-992 Add a transaction/locking mechanism to settings objects

This can cut the FTB loading by ~66% - worth it, but not ideal.
Real solution will have to be implemented later.

logic/BaseInstance.h

@@ -132,7 +132,7 @@ public:
 	 * This settings object stores instance-specific settings.
 	 * \return A pointer to this instance's settings object.
 	 */
-	virtual SettingsObject &settings() const;
+	virtual SettingsObjectPtr settings() const;
 
 	/// returns a valid update task
 	virtual std::shared_ptr<Task> doUpdate() = 0;